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TECHNICAL BRIEFS

Thermal Conductivity of Single-Walled Carbon Nanotube/PMMA Nanocomposites

[+] Author and Article Information
Csaba Guthy, Stijn Brand

Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104-6272

Fangming Du

Chemical and Biomolecular Engineering, University of Pennsylvania, 220 South 33rd Street, Philadelphia, PA 19104-6393

Karen I. Winey

Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104-6272; Chemical and Biomolecular Engineering, University of Pennsylvania, 220 South 33rd Street, Philadelphia, PA 19104-6393

John E. Fischer1

Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104-6272fischer@seas.upenn.edu

1

Corresponding author.

J. Heat Transfer 129(8), 1096-1099 (Mar 05, 2007) (4 pages) doi:10.1115/1.2737484 History: Received June 28, 2006; Revised March 05, 2007

Abstract

Single-walled carbon nanotubes (SWNTs) are considered as promising filler materials for improving the thermal conductivity of conventional polymers. We carefully investigated the thermal conductivity of SWNT poly(methylmethacrylate) (PMMA) nanocomposites with random SWNT orientations and loading up to $9vol%$ using the comparative technique. The composites were prepared by coagulation and exhibit $∼250%$ improvement in the thermal conductivity at $9vol%$. The experimental results were analyzed using the versatile Nielsen model, which accounts for many important factors, including filler aspect ratio and maximum packing fraction. In this work, the aspect ratio was determined by atomic force microscopy (AFM) and used as an input parameter in the Nielsen model. We obtained good agreement between our results and the predictions of the Nielsen model, which indicates that higher aspect ratio fillers are needed to achieve further enhancement. Our analysis also suggests that improved thermal contact between the SWNT network and the matrix material would be beneficial.

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Figures

Figure 1

Bundle length and diameter distributions of SWNT/DMF suspension used in the preparation of the composites. The length distribution was compiled from several 5μm×5μm AFM scans of surface treated Si wafers dipped into the SWNT/DMF solution. The diameter distribution is derived from a large number of line scans. The mean bundle diameter and length are 14.2 and 372nm, respectively, giving an estimated aspect ratio of 26.

Figure 2

Experimental thermal conductivities of SWNT-PMMA composites as a function of nanotube loading, and comparison with the predictions of the Nielsen model. The circles represent the experimental data; squares are the average values for nominally identical nanotube loadings. Dashed and solid curves are the predictions of the Nielsen model for aspect ratios of 26 and 20, respectively, assuming SWNT thermal conductivity=6000W∕mK. To obtain better agreement using the measured aspect ratio ∼26, an effective SWNT κ of 10W∕mK must be chosen (dotted curve).

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